Spine surgery rates in the United States exceed those in most developed countries by at least twofold. Furthermore, they increased 55 % during the 1980's. Wide geographic variations in surgical rates may imply professional uncertainty about optimal indications. Recent technical changes in spine surgery, including new spinal implants and a shift towards ambulatory surgery, may affect surgical rates and reoperation rates. The goals of this project are to examine whether surgical rates continue to rise, and if the introduction of interbody fusion cages resulted in acceleration of surgery rates: to examine surgical rates among the elderly and for spinal stenosis in particular to examine whether reoperation rates are increasing over time; and to determine if certain surgical procedures are associated with unusually high rates of reoperation. The analyses will make use of existing survey and administrative data. We will use a previously validated algorithm for identifying patients with lumbar spine surgery from automated data, as well as a previously validated comorbidity index. National rates of surgery will be examined using the National Hospital Discharge Survey and the Healthcare Cost and Utilization Project, both available from the National Technical Information Service, Examination of rates and trends among elderly patients, and especially for spinal stenosis, will make use of these national databases and of Medicare claims data for selected years. The analysis of reoperation rates will depend largely on a Washington State hospital discharge registry which will provide data from 1987 through 2000. Reoperation rates will also be examined using Medicare claims data. Finally, we hope to examine the growth of ambulatory disc surgery, which became increasingly popular after 1994. Although previously available surveys of ambulatory surgery are no longer available, we will have an opportunity to examine the growth of the ambulatory surgery using Medicare claims data, and some state ambulatory surgery databases. This series of analyses is important because it will help to clarify factors associated with changes in surgical rates. It will also help to assess the impacts of recent technical and practice innovations. Reoperation is generally regarded as an unfavorable outcome of lumbar spine surgery, and rising reoperation rates would be alarming. Thus, rates and trends in the use of spinal surgery and repeat operations may help identify high priorities for research, suggest areas requiring a more consistent therapeutic approach, and indicate possible problems in quality of care.